Can I take a friend to small clams court for personal loan not paid?

Yes, you have a Small Claims Court case for your friend's failure to comply with the terms of the written agreement to pay the loan by the due date.  Your lawsuit should include the $300 plus interest and court costs.  Court costs include the court filing fee and service of process fee (process server or certified mail cost).  If you use a process server (to provide notice of your lawsuit to the defendant), it is preferable to use a private process server instead of the marshal because the marshal will make a limited attempt to serve the defendant and if unsuccessful will not refund the fee.